Patent literature 1: US 2010/0191156 A1 (corresponding to Japanese Patent No. 5302193 and WO 2009/001558)
For example, patent literature 1 discloses a state estimation device, which monitors an involuntary eye movement of a monitoring target and estimates a state of the monitoring target according to whether an occurrence frequency of the involuntary eye movement is matched with a database.
The inventors of the present disclosure have found the following.
The conventional state estimation device may require a period of time for several tens of seconds before an occurrence frequency of the involuntary eye movement is detected.